My 40" Sony Bravia is about 12 feet from where I sit and that is about the right size for me. Much bigger and I would have to turn my head from side to side to see everything. A 65" screen would be way too big for me. Much smaller than 40" and my old eyes would start to have trouble focusing on the text, although I really don’t care to read the million and one ways in which a pharmaceutical or modern day "snake oil" concoction can turn me into a zombie or worse. I would pay big money for a Big Pharma and Snake Oil advertisement blocking feature though!
I'm glad my Sony Bravia is still working great even though I bought it in 2008. It doesn't have any of the modern features like smart TV apps, WiFi, BT, or even a USB port, and definitely no 4K just 1080, but the picture blows away pretty much all of those new cheap sets I’ve seen. You do get what you pay for and I paid a king's ransom for my Bravia 11 years ago, but it still works all these years later. I’ve got a cheap 26" Vizio in my study and it is okay for occasional viewing but its smart TV apps are long since way out dated as most never get updated by Vizio, and I prefer to hookup a Fire TV dongle and Roku dongle to using the built in smart TV features. Personally, I think all that smart TV stuff is mostly gimmicky and I do better with plug-in Fire TVs and Rokus. The set top boxes and dongles can be upgraded to better models in years to come, but you are pretty much stuck with the processors/RAM/etc. that came on the smart TV, so if it sucks now with apps it will suck even worse in the future. But to each there own of course.